Grinding apparatus



4 Sheets- Sheet 1 INVENTOR @7746 dbkzflsoi'z BY ATTORNEY? Feb. 11, 1941. M. H. JOHANSON GRINDING APPARATUS Filed Aug. 24, 1938 4 Sheets- Sheet 2 V w W Y R d M m R N.@ m m H 5Y W8 W 4 w a GNU Feb. 11, 1941. H; JOHANSON 2,231,762

GRINDING APPARATUS Filed Aug. 24, 1938 4 Sheets-Sheet 3 Feb. 11, 1941. M. H. JOHANSON ,231,762

GRINDING APPARATUS Filed Aug. 24, 1958 4 Sheets-Sheet 4 w g/4% dbkcz 715071 ATTORNEYXV Patented Feb. 11, 1941 UNITED STATES PATENT OFFICE GRINDING APPARATUS tion of New York Application August 24, 1938, Serial No. 226,495

Claims.

The present invention relates to apparatus for forming a curve or round on an article such as a cutting tool and in particular, it relates to apparatus for grinding a round on the blades of a 5 facesmill gear cutter.

When the side and top surfaces of a tool, such as a gear cutting tool, join at a sharp angle, there is a tendency in use for the tool to break down and wear away at the point of juncture of the two surfaces. It is customary, therefore, to grind a round or radius on face-mill gear cutter blades'and similar tools so as to avoid having a sharp point at the juncture of the top and side cutting edges of the blades.

Heretofore, the round or radius has been ground on a blade simply by positioning a cylindrical grinding wheel so that its active surface is inclined to both the top and side edges of the blade and then rotating the wheel in engagement with the blade. With this method, the round or radius produced on the blade is caused by the breakdown of the wheel. It varies therefore with wheels of different hardnesses and it cannot be controlled with the precision that is ordinarily desired in the manufacture of gear cutting tools. Moreover, the grinding wheel wears rapidly and i has a relatively short life.

The purpose of the present invention is to provide an accurate, completely controllable process and apparatus for grinding a round on a cutter blade or any article where -a round is desired at the juncture of two surfaces.

A further objectof the invention is to provide a device which is especially suited for the grinding of a round at the juncture of the top and side surfaces of a relieved face-mill cutter blade.

Still another object of the invention is to provide a process and apparatus for grinding rounds in which the grinding wheel will have relatively long life.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In grinding a round'on a blade or other article according to the present invention, a grinding wheel having an active surface of curved profile is employed and the round is produced by a generating movement of the rotating wheel in a curved path fro-m the side to the top of the blade or other article. Preferably the wheel used is dressed so that it has an active surface of circular arcuate profile and the round is pro-- duced by swinging the wheel in a circular arcu-' ate path from one side over the top of the blade.

The desired motion can be obtained by mounting the wheel upon a plate that is pivotally connected by a pair of parallel links with a fixed base. When the slide is moved on the base, then, every part of the slide including the grinding wheel moves parallel with itself in a curved path 5 and the wheel generates a curve on the blade as it rotates in engagement with the blade and swings from one side across the top of the blade.

By varying the radius of the active surface of the wheel, the radius of the round formed on 10 the blade can be varied.

When the article, that is being ground, is a relieved cutter blade, the round is preferably put on the blade by imparting the usual relieving motion to the blade while moving the rounding wheel over the side and tip of the blade. Thus a round will be produced on the blade which will follow the relieved top-surface of the blade and be correct throughout the whole useful life of the blade.

An advantage of the process of the present invention is the long life of the grinding wheel. The contact point between the wheel and the blade, which is being ground, moves over practically the Whole of the wheel surface during passage of the wheel from the side to the top of the blade and thus the wear is distributed over substantially the whole of the active surface of the wheel.

One embodiment of the invention is illustrated in the accompanying drawings in which:

Fig. 1 is a diagrammatic view illustrating the principle of operation of the apparatus of the present invention and showing one embodiment thereof;

Fig. 2 is a diagrammatic view on an enlarged scale, further illustrating said principle and showing the motion of the grinding wheel itself in grinding a round on a blade;

Fig. 3 is a plan view showing apparatus built according to another embodiment of the invention mounted on a relieving grinder of standard construction for grinding a round on the blades of a face-mill gear cutter;

Fig. 4 is a side elevation, with parts broken away, of this apparatus; and

Fig. 5 is a section through the apparatus taken in a plane at right angles to theplane of Fig. 4.

The principle of operation of the apparatus of the present invention is illustrated in Figs. 1 and 2. l0 denotes the face-mill gear cutter whose blades H are to be provided with a round. For the purposes of illustration, we have shown the apparatus set up to provide a round at the juncture of the inside surfaces I12 and the top surfaces l3 of the blades. It will be understood, however, that with the apparatus of the invention rounds may be formed at the junctures of both the outside and the top and of the inside and the top cutting edges of the blades if desired.

The grinding wheel W used for grinding the round is preferably dressed so that its active surface I5 is of circular arcuate shape. The center of curvature of the arc |5 is denoted at H5 in Fig. 2. The grinding wheel is mounted to rotate on an axis [8 and may be secured to the armature shaft of a motor I9 that is fastened to a plate 20. The plate 20 is connected by means of two parallel links 2| with a relatively stationary base 23. Each link 2| is pivotally connected at one end to the plate, as by means of pins 24, and each link is pivotally connected at its opposite end, as by means of pin 25, to the base 23.

To move the plate on the base, a screw 26 is provided. This screw is journaled in the base 23 and threads into the slide 20. It may be manipulated by a knurled knob 21.

It will be seen that as the screw 26 is rotated, the slide 28 will be swung with a parallel motion about the pivots 25 of the links 2| and each part of the slide will have a parallel motion. The paths of movement of the pins 24 in this swinging movement are indicated at 3| and 3|, respectively, and the center of curvature H; of the active surface I5 of the grinding wheel will travel in this swinging movement in an arc 30 which is parallel to the arcs of swing 3| and 3| of the pivot pins. As a result, a round 33 will be generated at the juncture of the side I2 and top |3 of the blade whose center is at 34, the center of the arc 30.

In Fig. 2, two extreme positions of movement of the grinding wheel are shown, one in full lines, the other in dotted lines. It will be noted that in the movement of the wheel from one position to the other, the point of contact between the wheel and the cutter blade moves from the position 35 to the position 35. In other words, the point of contact moves substantially across the full width of the wheel during the grinding of the round. Hence, as already stated, the wear is distributed over substantially the full width of the wheel.

The action of the wheel in grinding the round is a true generating action and the round produced upon the blade is the envelope of sucessive positions of the wheel in its swing.

By reason of the parallel movement of the wheel, the radius of the are 30 will be equal to the radius of the arcs 3| and 3|, that is, it will be equal to the length of the links 2| between the pivots 24 and 25. It is very easy, then, to control the radius to be ground on the cutting blade. By dressing the wheel to a different radius from the radius 35-|6 shown, the portion of the distance 34-|6 represented by the radius of the grinding wheel can either be increased or diminished and hence the portion of the distance 34-35 represented by the radius of the round on the blade can be either decreased or increased. Thus, complete control is had over the radius of the round which it is desired to produce upon the blade without changing the length of the links 2|.

A face-mill gear cutter has a plurality of cutting blades. To grind the rounds on all of these blades simultaneously, the cutter is rotated a plurality of times under the grinding wheel. The plate 29 may either be moved step by step for each revolution of the cutter or the screw 26 may be turned continuously at a very slow rate as the cutter rotates at relatively high speed under the moving wheel. It has been found in practice that entirely satisfactory results can be obtained with the continuous movement of the wheel and since this is a faster operation, is ordinarily preferred.

In practice the apparatus is mounted on the relieving grinder on which the blades of the cutter are relief-ground and the relieving motion of the machine is employed during the grinding of the rounds on the blades so that, as previously stated, a round may be ground on each blade which will follow the top-relieved surface of the blade.

In Figs. 3 to 5 inclusive, I have illustrated an organized practical embodiment of the invention for grinding rounds on the blades of a face-mill gear cutter. The apparatus is here shown mounted on a face-mill relieving grinder of standard construction. The cutter to be ground is denoted at C and its blades at B.

The cutter is secured in any suitable manner to the work spindle 36 of the relieving machine. This spindle is mounted for rotary and reciprocating movement in the work head 31 of the machine. The rotary movement is produced by the worm 38 and wormwheel 39. The reciprocatory movement is produced by the relieving cam 32 which engages the end face of the spindle. The cam 32 is of the usual construction and is rotated in time with the wormwheel 39 through the spur gears 49 and 54, the worm 51 and wormwheel 62. The cam 32 imparts a reciprocation tothe cutter spindle for each blade of the cutter to be ground.

The grinding wheel, which is to be employed for grinding the rounds on the blades of the cutter is denoted at 40. It is secured to the armature shaft of a motor 4| that is mounted upon a base or plate 42 in any suitable manner. The base 42 is pivotally connected by means of a bolt or pin 43 with the upright wall 44 of a plate 45.

The wall 44 is provided with two kerfs or recesses 46 at opposite sides, respectively, of the pivot 43 and equidistantly spaced therefrom. These recesses are arranged to receive selectively the clamping bolt 48 which is adapted to be threaded into a hole 49 in the motor base 42 and which is provided for fastening the motor base 42 to the wall 44. The motor base 42 is adapted to be swung through an angle of about the pivot 43 to position the grinding wheel 4|! in engagement with either the outside or the inside surface of a cutter blade and the base can be secured in either position by passing the clamping bolt 48 through the proper recess 46. The wall 44 has its upper face shaped more or less on an are about the pivot 43 as a center, as clearly shown in Fig. 5. In the drawings, the motor base is shown in position for the wheel to round off the corner at the juncture of the inside and top edges of the blades B.

The plate 45 is connected by means of two pins 53 with the parallel arms 5| of a pair of studs 52. The studs 52 are mounted in bushings 53 that are secured in suitable openings in a base plate 55. The bushings 53 also extend down into suitable recesses formed in an angularly adjustable plate 56 so that the base 55 is held against movement relative to the plate 58.

There is a screw 58 threaded into the base 55 that is manipulated by a knurled knob 59. This screw is provided with acollar 60 that engages in a kerf 6| that is formed in the under face of the plate 45. Asthe screw- 58 is rotated, then, the plate 45 is moved on the base 55 being swung about the parallel studs 52*through the parallel linkage 5|59.- The plate 45 and grinding wheel 40 have, then, the parallel movement already described with reference to the diagrammatic showing of Figs. 1 and 2. The p1ate45 is held on the base 55 by gibs '63'and screws 64'.

The plate '56is mounted on a slide 65 for angu lar adjustment about a stud 61, which is mounted in a bushing 98 in the plate 55 and threads into the slide 65. The angular adjustment of the plate 5B'on'the slide'65'i's made manually and may be determined by'means of scales I9 and 1| provided on the plate'56 which read against an indicator pin 12 that is secured in the slide (i5. After the adjustment has been made, the plate 56 is clamped.- to the slide 65by the T-bolt 13 which engages in an arcuate T-slot 14 "that is formed in the upper face of the slide 65.

The slide 65 is mounted for rectilinear adjustment on a cradle 75. This adjustment is effected by rotation of the screw 16 which may be manipulated by a knurled knob 11. "The screw 151s secured in a dependentportion 78 of the slide 65 and threads into a nut 19 that is secured in the cradle 15. The slide 65 is provided with a dovetailed way or recess that engages a dove-tailed guide portion 89 of the cradle 75 to guide the slide 65 in its movement on the cradle, as clearly shown in Fig. 4.

The cradle 15 is formed on its under face with arcuate guide surfaces 82. These are adapted to slide on a corresponding arcuate surface 83 formed on the upper face of a slide 95. The eradle 75 is adapted to be manually adjusted on the slide 85 and is adapted to be secured in any adjusted position by T-bolts 86 which engage in arcuate T-slots 8! that are-formed in the under face of the cradle.

The slide 85 is mounted for rectilinear adjust ment on an arm 99. This adjustment is effected by rotation of a screw 9| that is mounted in the dependent portion 92 of the slide 85 and. that threads into a nut 93 which is secured to the arm 99. The screw 9| can be manipulated by a knurled knob 95. The rectilinear adjustment of the slide 85 on the arm is in a direction at right angles to the direction of adjustment of the slide 65 on the cradle 15. The slide 85 is formed with a dove-tailed recess to receive the dovetailed guide way 88 of arm 90'to guide the slide 85 in its adjustment on the arm.

The arm- 99 is mounted by means of bushings 93 on a stud 94 for pivotal movement about the stud. The stud is mounted in ears 95 that are integral with the work head or other part of the relieving grinder on which the apparatus of the present invention is mounted. The arm 90 can be swung about the stud 94 to move the grinding apparatus to or from operative engagement with the cutter C which is to be ground.

A hooked rod 98 is provided to hold the arm 90 and the grinding apparatus mounted thereon in operative position. The hook at the inner end of this rod is adapted to engage over a lug 99 that is provided on the machine. The hookedrod 98 is moved to and from engaging position by movement of the handle 91. This handle is secured to a shaft I00 that has a pin I02 eccentrically mounted in its lower end which engages in a recess or slot I93 cut in the rod 98.

The arm 99 can be adjusted vertically on the stud 94 by rotation of a pin 96 that threads into the arm. The'lower end of this pin seats against the upper face of the lower ear 95 in which the stud is mounted.

The adjustment of the slide 85 on the arm 99 permits of adjusting the grinding wheel in accordance with the diameter of the cutter whose blades are to be ground. The adjustment of the cradle 75 on the slide 85 permits of inclining the grinding wheel in accordance with the top relief angle a (Fig. 3) of the blades to be ground so that the grinding wheel will correctly round off the corners of the blades for the full length of the.

blades as the blades pass under the rotating grinding wheel. The adjustment of the slide 65 on the cradle [5 permits of adjusting the grinding wheel in accordance with the height of the blades to be ground. The adjustment of the plate 56 on the slide 65 permits of adjusting the grinding wheel to secure any desired position of the center of the arc of the round, which is to be ground on the blades. The adjustment of the motor base 42 on the wall 44 of the plate 45, as already described, permits of swinging the grinding wheel from one side to the other of the blades to permit grinding the round at the juncture of the inside and top or of the outside and top surfaces of the blades.

When all of the adjustments have been made, the machine is started. The cutter rotates on its axis and. is simultaneously reciprocated by the cam 32. The grinding wheel 49 is rotated on-its axis by the motor 4| and simultaneously the grinding wheel may be moved in its desired curvilinear path by slowly rotating the screw 58. The screw moves the plate 45 on the base 55, producing the previously described parallel movement of the grinding wheel to cause the grinding wheel to generate a round on the blade. As already stated, the cutter will make a number of revolutions for a passage of the grinding wheel from one end to the other of its movement. The movement of the wheel may be intermittent, that is the screw 58 may be turned slightly for each revolution of the cutter or it may be made continuous and the screw turned continuously but at a very slow rate.

Because of the relieving movement of the cutter, each blade of the cutter Will be advanced axially toward the grinding wheel 40 as it rotates under the wheel and thus the round ground on the blade will follow the top surface of the blade and will be uniform for the Whole length of the blade. Hence the round will be correct for the full life of the blade. Thecam 32 is, as stated, a standard relieving cam and the cutter is advanced toward the wheel and withdrawn again once for each blade of the cutter to be ground. The withdrawal motion returns the cutter to original position, after one blade has been ground, so that the next blade may be in position to start its grinding.

The round produced on a cutter blade by the apparatus of the present invention will be very smooth and its radius can accurately be controlled. Moreover, wear is distributed over a very large surface of the wheel and the wheel will have a very long life.

While the invention has been described in connection with the grinding of blades of a facemill gear cutter, it will be understood that it may be employed in grinding rounds on any cutting tool. In fact, it may be employed wherever it is desired to grind a round on an article. Thus, it may be employed for grinding a round at the juncture of the top and a side surface of a gear tooth. Many other uses for the invention will readily occur to those skilled in the art. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall Within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. Apparatus for grinding convex rounds on the blades of a face-mill gear cutter at the junctures of the tops and the side faces of the blades, comprising a support, a base adjustable on the support, a plate, means for connecting the plate to the base comprising a pair of parallel link members, each of which is pivotally connected at one end to the plate and at its opposite end to the base in such way that the points of pivotal connection with the base lie nearer to the work than the points of pivotal connection with the plate, a rotary grinding wheel having an active surface of convex circular arcuate profile in an axial plane journaled on the plate, means for adjusting the base angularly on the support in accordance with the top clearance angle of the of the blade to be ground, means for rotating the wheel, means for moving the plate relative to the base to cause it to swing about the points of pivotal connection of the links with the base, means for rotating the cutter on its axis, and means for simultaneously reciprocating the cutter axially once for each blade to be ground.

2. Apparatus for forming a convex round on a gear cutting tool at the juncture of a side face and the tip of the tool comprising a support, a slide adjustable rectilinearly on said support, a cradle adjustable angularly on said slide, a second slide adjustable rectilinearly on the cradle in a direction at right angles to the direction of adjustment of the first slide, a base adjustable angularly on the second slide about an axis at right angles to the axis of adjustment of the cradle, a plate movably mounted on the base and pivotally connected to the base by a pair of parallel links, each of which is pivotally connected at one end to the base and at its opposite end to the plate, the first-named pivotal connection lying between the second-named pivotal connection and the work, a grinding wheel journaled on the plate, means for rotating the wheel, and means for moving the plate on the base about the first-named pivotal connection to grind a convex round on the tool.

3, In apparatus for grinding convex rounds on the blades of a face-mill gear cutter at the juncture of a side face and the tip of a blade, a work support, a grinding wheel having a curved profile. in an axial plane, means for adjusting the wheel relative to the work support so that the axis of the wheel is inclined to both the side surface and the tip of a blade of the cutter, means for rotating the work support, means for reciprocating the work support axially during its rotation once for each blade of the cutter to be ground, means for rotating the grinding wheel, and means for displacing the grinding wheel bodily in a curved path, during a plurality of revolutions of the work, about a center representing the center of the round to be ground.

4. In apparatus for grinding convex rounds on the blades of a face-mill gear cutter at the juncture of a side face and the tip of a blade, a work support, a grinding wheel having a circular arcuate profile in an axial plane, means for adjusting the wheel relative to the work support so that the axis of the wheel is inclined both to the side face and the tip of a blade, means for rotating the work support, means for reciprocating the work support axially during its rotation once for each blade of the cutter to-be ground, means for rotating the grinding wheel, and means for displacing the grinding wheel bodily, during a plurality of revolutions of the work, in a circular arcuate path the radius of curvature of which is equal to the radius of curvature of the profile of the grinding wheel plus the radius of curvature of the round to be ground on the work.

5. The method of grinding convex rounds on the blades of a face-mill gear cutter at the junctures of the sides and the tips of the blades which comprises employing a rotary grinding wheel that has an active surface of convex circular arcuate profile shape in an axial plane, mounting said wheel in engagement with the cutter so that the axis of the wheel is inclined to both the side and the tip of a blade, rotating the wheel on its axis, and swinging the wheel bodily in a circular arcuate path in a plane perpendicular to the tip of the tool, while rotating the cutter on its axis and simultaneously reciprocating the cutter relative to the wheel in a direction axial of the cutter, the radii of curvature of the wheel profile and of said path being so selected that the radius of curvature of the path less the radius of curvature of the wheel profile equals the radius of the round to be ground on the blades.

MAGNUS H. JOHANSON. 

